Ureteral stents are widely used to facilitate drainage in the upper urinary tract (e.g., from the kidney to the bladder), for example, following ureteroscopy, endourerotomies, and endopyelotomy for ureteral strictures, as well as in other instances where ureteral obstruction may occur, for example, following lithotripsy.
A schematic diagram of a stent 10 in accordance with the prior art is schematically illustrated in FIG. 1. The stent 10 comprises an elongated stent body in the form of a tubular polymeric extrusion including a renal coil 14, bladder coil 16, and a substantially linear shaft 12 between the coils 14, 16. The stent 10 shown is further provided with the following: (a) a tapered distal tip 10k, to aid insertion, (b) multiple side ports 18 (one numbered), which are arranged in a spiral pattern along the length of the stent body to promote drainage, (c) graduation marks 13 (one illustrated), which are used for visualization by the physician to know when the appropriate length of stent has been inserted into the ureter, and (d) a Nylon suture 22, which aids in positioning and withdrawal of the stent, is provided at the proximal end 10b of the stent, as is known in that art. During placement, the ureteral stent 10 may be placed over a guide wire, through a cystoscope and advanced into position with a positioner.
Referring now to FIGS. 1 and 2, once the distal (kidney) end 10k of the stent is advanced into the kidney 19, the guide wire is removed, allowing the coils 14, 16 to form in the kidney 19 and bladder 20. As shown in FIG. 2, the stent 10 extends through the ureteral orifice 21a and into the bladder 20. For clarity, the ureter entering bladder 20 through the opposite ureteral orifice 21b is not shown.
Such stents, however, are commonly associated with pain and discomfort in the bladder and flank area after insertion. One way to minimize pain and discomfort is to orally administer drugs to the patient. Commonly prescribed oral drugs are opioid analgesia (e.g. Vicodin® and Percocet®), which are controlled substances and have the potential for abuse by patients.
Another way to address pain and discomfort is to release a therapeutic agent from the ureteral stent. See Pub. Nos. US 2003/0224033 to Li et al., US 2006/0264912 to McIntyre et al., US 2009/0187254 to Deal eat al., and US 2009/0248169 to Li et al.